In systems including a transmitter, a link (e.g., a serial link) coupled to the transmitter, and optionally also a receiver coupled to the link, it is desirable to include device detection circuitry in the transmitter. The device detection circuitry determines whether a receiver is coupled to the link. Such device detection circuitry is especially desirable in storage applications in which the receiver is a storage device and the transmitter is a controller.
When both the transmitter and receiver are transceivers, it is often useful for both transceivers to include device detection circuitry. Device detection circuitry (in a transceiver coupled to a link) should be capable of determining when another device is coupled to the link without causing any electrical damage to the input or output circuitry of the transceiver.
For example, systems that comply with the “Digital Visual Interface” (“DVI”) standard (adopted by the Digital Display Working Group) exploit a proprietary electrical configuration which generates different common mode levels at both sides of a differential link depending on device presence.
The expression “differential link” is used herein, including in the claims, to denote a link over which at least one differential signal can be transmitted.
The expression “serial differential link” herein denotes' a serial link that is a differential link and thus comprises a conductor pair for transmitting a differential signal. The differential signal is typically a voltage (the potential on one conductor of the pair minus the potential on the other conductor of the pair).
The expression “parallel differential link” is used herein to denote a parallel link that comprises two or more differential links, each differential link comprising a conductor pair for transmitting a differential signal.
The term “transmitter” is used herein in a broad sense to denote any device capable of transmitting a signal (for example, a signal indicative of data) over a link (and optionally also performing additional functions, which can include encoding and/or encrypting data to be transmitted and other operations related to encoding, transmission, or encryption of data). The term “receiver” is used herein in a broad sense to denote any device capable of receiving a signal that has been transmitted over a link (and optionally also performing additional functions, which can include decoding and/or decrypting of received data and other operations related to decoding, reception, or decryption of received data). For example, the term transmitter can denote a transceiver that performs the functions of a receiver as well as the functions of a transmitter.
In some embodiments, the invention is implemented in a device (typically a transceiver or other transmitter) coupled to a serial differential link. In some such embodiments, communication between the device and each other device coupled to the serial differential link is in compliance with the “SATA standard” (the standard known as Serial ATA, Revision 1.0, adopted on Aug. 29, 2001, by the Serial ATA Working Group) for communication between a host and one or more storage devices over one or more serial differential links.
In a class of preferred (“SATA-compliant”) embodiments of the invention, the invention is a system including devices configured for communication over at least one serial differential link in compliance with the SATA standard, wherein at least one of the devices includes a device detection circuit that embodies the invention. In some other embodiments, the invention is a SATA-compliant device that includes a device detection circuit that embodies the invention.
The term “termination” is used herein, including in the claims, to denote circuitry which, when coupled to a link, terminates the link with a specific impedance. A termination can consist only of resistive elements so that the impedance is a resistance. Alternatively, a termination comprises at least one resistive element and/or at least one capacitive element and/or at least one inductive element. The term “differential termination” is used herein, including in the claims, to denote a termination configured to be coupled to a differential link to terminate each conductor of the differential link with a specific impedance. A differential termination has a branch for each conductor of the differential link.